Newbie to Maven build tool

I had successfully installed Maven in my machine , and used this command and this in process of building for a long time .

mvn archetype:create -DgroupId=com.mycompany.app -DartifactId=my-app
from command line . But i don't understand what is the meaning of this command and what it will do . Please tell what is happening here.

The "long time" part is a one-time issue. One of Maven's greatest strengths is its ability to download and cache copies of all the resources needed to do a Maven build. I have one project where 1.5MB of project ends up building a 30+MB distributable. But downloading those other 28.5MB over my fairly slow Internet connection takes time when doing that first build. Subsequent builds are MUCH faster!